So here's your guide anon.
- Make a github account and open https://github.com/vg-mjg/mjg-repo
- Open the file you want to change, and press edit
- Edit what you want
- Explain what you did and press "Propose changes"
- Create pull request
- Explain pull request
- Wait for repoanons to merge into the main repo
- ???
- Profit!
A better way to do this is working on your own fork.
- Check your repositories and open it (you have it if you did method A, or simply press the "fork" button on mjg-repo)
- Make some changes, then press contribute -> open pull request
- Create pull request
- Explain pull request
After method A or B you'll become official repoanon, which means you won't have to bother about making pull request as you'll have direct access to the repo.
Which means you'll see something like pic related if you edit a file
It's still a good idea to make pull requests if you do something big.
If you're a brainlet there is https://desktop.github.com/ to make things easier.
Good luck.